Method for transmitting data from an emitter to a plurality of receivers

ABSTRACT

A method is provided for transmitting data from a sender to a number of receivers. Also provided are an emitting and/or receiving unit and a communication system. The present invention seeks to provide a method, an emitting and/or receiving unit and a communication system for the efficient, resource saving and energy saving transmission of data to a group of receivers of a point-to-multipoint service. To this end, a point-to-multipoint service is carried out as an extension of a broadcast service CBS in a multi-layer protocol system, providing a multimedia transmission and/or a multicast service, preferably in the form of a multimedia broadcast/multicast service MBMS, during the distribution and/or planning of the use of system resources and the use of a discontinuous reception DRX.

BACKGROUND OF THE INVENTION

The present invention relates to a method for transmitting of data froma sender to two or more recipients, to a transmitting and/or receivingunit, and to a communications system.

In the case of many services and applications which are offered inmodern mobile radio systems, the aim is to transmit messages not just toone mobile radio subscriber but to two or more mobile radio subscribers.Examples of services and applications such as these include news groups,video conferences, video-on-demand, distributing applications, etc.

Where messages are being transmitted to the various subscribers, it ispossible to send each recipient a copy of the data separately. Althoughthis technique can be implemented easily, it is not suitable for largegroups, however. Since the same message is transmitted to a total of Nrecipients via individual connections or unicast connections, and istransmitted a number of times in the process over common connectingpaths, this method requires a very wide bandwidth.

A better option is offered by multicast transmission. In this case, thevarious subscribers to which the same message is intended to betransmitted are combined to form a multicast group, which is allocated amulticast address. The data to be transmitted is then sent only once tothis multicast address. The MC message is in the ideal case sent onlyonce from the sender to the recipients via common connecting paths. Thesender does not need to know where and how many recipients are concealedbehind the multicast address.

In the case of broadcast, messages are sent to all the subscriberswithin a geographical region. A region such as this may, for example, bedefined by a part of the overall network. As in the case of multicast,the broadcast message is ideally sent only once via common connectingpaths from the sender to the recipients. Each subscriber has to carryout enabling settings on their respective terminal if he/shesubsequently wishes to evaluate broadcast packets from a correspondingbroadcast group. The subscriber can then determine whether he/she wishesto receive or reject all of the broadcast messages, or to receive onlyspecific messages.

In the course of a known method for data transmission, a specific numberof frames are typically always interchanged between a network and amobile radio within a specific time. A frame is in this case a timestructure on which, for example, in the case of UMTS, all of the signalprocessing and data transmission is based, see also [1].

If all of the frames are transmitted and received by the mobile radiocontinuously, this is referred to as continuous transmission orcontinuous reception. However, it is also possible, for transmission, touse interrupted reception or so-called discontinuous reception DRX inorder, for example, to reduce the energy requirement of the mobileradios. When using DRX, the frames are not transmitted and received bythe mobile radio continuously, but rather specific frames are omitted.In this mode, however, at least one specific subset of all of the framesor a subset of the possible frames must be transmitted in order tomaintain the connection.

The present invention is, therefore, directed toward a method, atransmitting and/or receiving unit and a communications system forefficient, resource-saving and energy-saving transmission of data to agroup of recipients on a point-to-multipoint service. In particular, isthe present invention seeks to allow use for the purposes of amultimedia broadcast/multicast service MBMS.

SUMMARY OF THE INVENTION

Accordingly, a method according to the present invention isdistinguished in that a point-to-multipoint service is provided in asystem with a multilayer protocol architecture as an extension to abroadcast service CBS by multimedia transmission and/or a multicastservice, preferably in the form of a multimedia broadcast/multicastservice MBMS, for allocation and/or planning of use of system resourcesand use of discontinuous reception DRX. Information is thus sent in anefficient form via the point-to-multipoint service, and is transmittedonly once in the process. In this case, for the purposes of the presentinvention, the expression “information” also refers to information whichis basically commercial or is sent without being requested; that is tosay, in particular, an offer, a commercial or an advertisement for a newproduct, and consumer information in some other form.

In the case of relatively complex, multilayer protocol architectures,such as the protocol stack in the Universal Mobile TelecommunicationsSystem UMTS, no functions have yet been included for group transmissionor point-to-multipoint transmissions which either are not defined or aredefined not only regionally. Since UMTS forms an essential field of usefor the present invention, the following text uses the description of anexemplary embodiment with reference to the figures of the drawing todescribe the protocol structure of UMTS, although the present inventionis not restricted to such application.

The planning for a method according to the present invention isadvantageously carried out in two stages: a first message is used tosignal where, how many and when resources are assigned for thetransmission of multicast messages. Accordingly, this messageadvantageously may be very short. The first message is preferably usedto transmit information elements with details about what resources ofthe transport channels or which frames of the physical channels arereserved or assigned for the transmission of messages. Signalingtherefore does not take place until the planning for the transmission ofa message, thus defining which physical channels and transport channelsare used for the transmission of messages. The method according to thepresent invention thus can be adapted in a very flexible manner. In thecase of UMTS, a common traffic channel CTCH is mapped in one embodimentof the present invention, on the basis of a requirement by the sender,onto other transport channels than the forward access channel FACH, andonto other physical channels than the secondary common control physicalchannel S-CCPCH.

Various protocol layers are configured on the basis of discontinuousreception DRX planning messages by the radio resource monitoring unitRRC; that is to say, by the RRC of a sender for unidirectionalconnections. Notification therefore is provided at a physical level of arecipient as to the resources in which data can be expected in an MCmessage or further planning messages. In this case, the messages aboutplanning and/or assignment of resources include, in one embodiment ofthe present invention, information about a respective multicast group,so that entire groups of recipients are informed. Groups such as these,particularly multicast groups, are preferably indicated by an MC groupaddress or an MC group identity.

Further information in a message is identified in a particularlyadvantageous manner in a monitoring layer in a recipient in order todecide whether an MC message with payload data should be received. Thus,for example, the only subscribers who are accessed are those who wish toreceive sports messages so that, by using this group identity,information and data are effectively prevented from being readunnecessarily by subscribers who have no interest in messages in thecorresponding group.

A first planning stage, MC DRX level 1, is used to signal which physicalchannels and transport channels will be used for the transmission of MCmessages. In other words, the resources which are used or reserved fortransmission of point-to-multipoint services, particularly the MBMSservice, are signaled and/or notified for the transmission of messagesand/or signaling data. This is preferably done in the DRX level 1message, and allows the subscriber terminal to be informed of whenmessages and/or signaling data, particularly the DRX level 2 messages,actually will be transmitted. This is also used to signal where and onwhat channels these messages will be transmitted. In one embodiment, abasic specification of the messages and/or signaling data is alsoproduced in order to decide whether this is a CBS, multimedia broadcastor multicast. The advantages of the respective indication, which islinked to a message, about the transmission channels and the fundamentalclassification of the information which can be expected will bedescribed in more detail in the following text. However, even when usingUMTS, it is possible for the CTCH to be mapped, on the basis of arequirement by the sender, onto other transport channels than the FACHand onto other physical channels than the S-CCPCH.

On the basis of the discontinuous reception DRX planning messages,various protocol layers are configured via the radio resource monitoringunit RRC, in particular by the RRC in a receiver. In this case, anotification is provided at a physical level as to the resources inwhich data in an MC message or further planning messages can beexpected. These messages about planning and/or assignment of resourcesinclude information about a respective multicast group. This furtherinformation in a message, inter alia relating to a group association, isidentified in a monitoring layer BMC in order to decide whether an MCmessage with payload data should be received. This information ispreferably signaled in the course of an MC DRX level 2 message, whichincludes information about the physical channels and transport channelson which MC messages actually will be transmitted as payload data.Alternatively, payload data contents also are signaled in the course ofan MC DRX level 2 message itself with details about resources via whicha multicast message subsequently will be actually transmitted.

In one preferred embodiment of the present invention, previouslyassigned indices are used as the basis for assigning or notifying whenMC messages are actually transmitted to resources of physical channelsand transport channels, such as frames, in which case an offset withrespect to a first frame which is used for an MC transmission, and/or alength of the CBS planning period, can be indicated.

Preferably, an information element also is transmitted in order todecide on reserved resources in resources for broadcast or multicastservices, so that the method according to the present invention can beused for both services.

Owing to the progress in miniaturization, the method according to thepresent invention is implemented in a mobile telephone as a transmittingand/or receiving unit, with a mobile unit preferably being designed tosend and/or receive multimedia messages. A corresponding communicationssystem also can cope with the relatively large amounts of data formultimedia message by virtue of the flexibility explained above.

Additional features and advantages of the present invention aredescribed in, and will be apparent from, the following DetailedDescription of the Invention and the Figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a simplified structogram illustrating a protocol stack inUMTS.

FIG. 2 shows an assignment of frames to a logical channel CTCH via whichcell broadcast messages are transmitted.

FIG. 3 shows an index layout as is used for CBS DRX, in order toallocate an index to sets of resources and frames.

FIG. 4 shows the information element that is used according to the priorart for signaling of the CBS DRX level 1 information as a detail from[3].

FIG. 5 shows the information element that is used according to the priorart for signaling the BMC scheduling message CBS DRX level 2 as a detailfrom [4].

DETAILED DESCRIPTION OF THE INVENTION

A protocol stack in the universal mobile telecommunications system UMTShas a multilayer structure and is subdivided into the physical layer,the data link layer and the network layer. The data link layer issubdivided into the sub-layers of medium access control MAC, radio linkcontrol RLC, packet data convergence protocol PDCP andbroadcast/multicast control MBC, as shown in the illustration in FIG. 1.The network layer includes two parts the radio resource control RRC anda duplication avoidance, with only the RRC layer also ending in the UMTSTerrestrial Radio Access Network UTRAN. The corresponding instance forthe duplication avoidance does not belong to the UTRAN, but is moved outto a core network CN. In the layer L3 and the RLC layer, a distinctionis drawn between a user plane N plane and a control plane C plane, withthe PDCP layer and the BMC layer belonging exclusively to the userplane. Ellipses between the layers symbolize the locations of theservice access points for communication with the respective partnerinstance, as defined in [2].

The RRC layer manages and controls the use of the radio equipment and,therefore, has connections via control service access points to all theother layers in order to control their configuration. These controlservice access points thus are not used for communication betweenpartner instances, but exclusively between layers in the same protocolstack. The connections between the RRC and lower layers are used forreception of measured values from the bit transmission layer and MAClayer as well as for controlling functions in the individual layers. TheRRC layer determines, for example, the nominal value of the inner powercontrol loop, which is implemented in the bit transmission layer.

The transmission via the air interface is provided via so-calledphysical channels. The transmission services in the physical layer areprovided at the service access points via so-called transport channels.Transport channels are characterized by how the data is transmitted. Thetransmission services for the monitoring and MAC layer are provided viathe logical channels. Logical channels are characterized by the type ofdata being transmitted. A distinction is, in this case, drawn betweenmonitoring data and traffic or payload data.

Various logical channels and transport channels are mentioned in thefollowing text, and therefore will be described briefly:

CBS messages are transmitted between the RLC and MAC via a logicalchannel which is called the common traffic channel CTCH. The CTCH isused for transmission of data in the user plane to all subscriberterminals UEs or to a group of subscriber terminals. The CTCH is aunidirectional point-to-multipoint channel in the downlink path, whichis mapped onto a transport channel or forward access channel FACH. TheFACH is a common transport channel on the downlink path and is used fortransmission of relatively small amounts of data. The FACH is thenmapped onto a physical channel which is called the secondary commoncontrol physical channel S-CCPCH. In principle, the S-CCPCH carriesinformation for the FACH and for one or more paging channels PCH. Theprimary CCPCH P-CCPCH transmits the BCH information.

The logical channel called the broadcast control channel BCCH is acommon channel for the downlink path, on which monitoring data is sentback to all the subscriber terminals in a radio cell. This monitoringdata is, for example, the system information blocks SIB. The BCCH ismapped either onto the FACH or onto the broadcast channel BCH.

The transmission of data with interrupted reception or so-calleddiscontinuous reception DRX already has been described in theintroduction as a known measure in order, for example, to reduce thepower consumption of mobile radios. DRX is used inter alia for the cellbroadcast service CBS which is specified in UMTS. The system-internalplanning as to when frames and/or resources are available for CBSservices and when these resources transport CBS messages is notified viaso-called scheduling information. This planning is carried out in twostages:

The first planning stage, CB DRX level 1, is intended to signal whatresources in the transport channel FACH and what frames in the S-CCPCHare in fact reserved and/or assigned for the transmission of cellbroadcast messages. This signaling is intended to be transmitted as partof the system information to the RRC via the logical channel BCCH. TheCB DRX level 1 message is used to signal how many frames are assignedfor the transmission of cell broadcast messages, and when. Theillustration in FIG. 4 shows an information element which is usedaccording to the prior art for signaling of the CBS DRX level 1information. CB messages then can be transmitted only in these frames.

The illustration in FIG. 2 shows an example of the assignment of framesto the logical channel CTCH via which the cell broadcast messages aretransmitted. An offset by two frames with respect to the frame No. 0, aperiodicity of the allocated resources of six frames and a total, of twosuccessive frames are assumed in this case. A mobile radio UE whichwishes to receive CB messages now does not need to check the contents ofeach frame, but only the contents of the frames with the numbers 2/3,8/9, 14/15, etc. This reduces the processing complexity and, at the sametime, the power consumption within the subscriber terminal.

CBS DRX uses an index scheme which allocates an index to the sets ofresources or frames, as is illustrated in the illustration in FIG. 3.The assignment of the resources in the second planning stage, whichfollows, then can be carried out very easily via these indices.

For the second planning stage, CBS DRX level 2, a so-called inbandscheduling message is transmitted together with the actual CB message onthe logical channel CTCH, and is evaluated by the BMC. This CBS DRXlevel 2 message is used to transmit various information to thesubscriber terminals, as shown in the illustration in FIG. 5, whichillustrates an information element which is used according to the priorart for signaling the CBS DRX level 2 information. The illustratedinformation also includes:

-   -   Information as to which of the resources notified in the CBS DRX        level 1 message actually will be used to transmit CB messages,        indicated by the resource indices that are used.    -   An indication is provided, inter alia, of any offset with        respect to the first frame that is used for transmission of MC        messages and the length of the CBS planning period; that is to        say, the number of successive resources.    -   Message type (CBS message or scheduling message).    -   Message identification (identification of source and type of the        CBS message).    -   Serial number. (Information for the subscriber terminal from        which it can determine whether it already has received a        specific message).    -   Coding scheme (information about the coding and language used).

The RRC and BMC use so-called primitives to interchange, inter alia,information about the configuration of the various planes and units.

After receiving an appropriate scheduling message, the BMC informs theRRC whether it should configure the physical level for reception of CBSmessages. The RRC then once again informs the BMC of the CTCHconfiguration settings carried out. Furthermore, information about dataflow measurements, inter alia, also is interchanged.

For introduction, according to the present invention, of discontinuousreception DRX for multicast or MC services, particularly in UMTS, thetechniques described above are adapted with the aim of making itpossible to use the characteristics of discontinuous reception DRX, asalready have been described for CB services, and for multicast or MCservices in UMTS, as well. The method according to the present inventionfor use of discontinuous reception DRX for multicast services isreferred to in the following text as MC DRX.

The planning for MC DRX, as to which resources are available for MCservices and when these resources will transport multicast messages, isnotified via appropriate messages, in a comparable manner to the CBS.The messages for the planning and assignment of the resources for thispurpose include, inter alia, information about the multicast groups. Inone embodiment, the multicast groups are indicated by an MC groupaddress or an MC group identity.

The planning for MC DRX as to which physical channels or transportchannels, frames and resources will be available for MC services, andwhen, as well as when these resources will transport multicast messagesis notified via so-called “scheduling messages” or planning messages.The various UMTS protocol layers are configured by the radio resourcemonitoring unit RRC on the basis of these planning messages. Theinformation, therefore, already is available at the physical level as tothe resources in which an MC message or further planning messages can beexpected. Furthermore, the BMC layer can evaluate further information inorder to decide which MC messages actually should be received. Theplanning is carried out in two stages, as described in the followingtext:

The first planning stage, MC DRX level 1, signals which physicalchannels and transport channels will be used for the transmission ofplanning information, in order to prepare for the transmission of MCmessages. This is because, in comparison to CBS, the CTCH for MCservices also is optionally mapped onto other transport channels thanthe FACH and onto other physical channels than the S-CCPCH. Furthermore,the MC DRX level 1 message is used to transmit information elements asto which frames in the physical channels are reserved or assigned forthe transmission of further planning information.

This signaling is transmitted as part of the system information to theRRC via the logical channel BCCH. The MC DRX level 1 message thussignals where, how many and when resources will be assigned for thetransmission of multicast messages. MC messages then can be transmittedonly in these frames.

According to the present invention, MC DRX makes use of an index schemein which indices are allocated to the sets of the resources inconjunction with the physical channels and transport channels that areused. The assignment of the resources in the second planning stage,which follows this, is then carried out very simply via these indices.

For the second planning stage, MC DRX level 2, a so-called “inbandscheduling message” is transmitted together with the actual MC message,and is then evaluated by the BMC. Various information is transmitted tothe subscriber terminals UE in this MC DRX level 2 message. Thisincludes, inter alia:

-   -   1. Information about which physical channels and transport        channels that are mentioned in the MC DRX level 1 message        actually will be used to transmit MC message.    -   2. Information about the resources which are notified in the MC        DRX level 1 message which actually will be used to transmit        multicast messages.    -   3. Message type, that is to say a distinction between an MC        message or a scheduling message.    -   4. Message identification (MC group address or MC group        identification, identification of the source and type of the MC        message).    -   5. Serial number (information for subscriber terminals, from        which they can tell whether they already have received a        specific message).    -   6. Coding scheme (information about the coding and language        used).

In the case of items 1 and 2 mentioned above, when using the describedindex scheme according to the present invention, the assignment andnotification as to when MC messages actually will be transmitted on theresources of the physical channels and of the transport channels can becarried out via the previously assigned indices. Otherwise, a differentallocation rule is stipulated. An indication also is always provided,inter alia, of any offset with respect to the first frame that is usedfor MC transmission and the length of the CBS planning period; that isto say, the number of successive resources.

For the situation where the already existing DRX for CBS is extended bythe functionality of supporting MC DRX, an information element isintroduced which is used to distinguish whether the reserved resourcesare resources for broadcast or multicast services. For example, the“message type” can be used to distinguish between a CBS message, an MCmessage, a scheduling message. etc.

The method according to the present invention can be adapted veryflexibly, by allocation of resources, to match the size of a message tobe transmitted. Thus, it also is possible to use the method according tothe present invention to send complex messages, such as messages with amultimedia content, so-called multimedia messages MM. The already sentlevel 1 and level 2 messages for planning and preparation fortransmission require considerably less transmission bandwidth thanmultimedia contents. The level 1 and/or level 2 message can betransmitted via a relatively narrowband channel wherein, in the case ofa communications system with two or more transmissions that take placesimultaneously, the overall available bandwidth can be distributedand/or assigned very effectively.

For this purpose, in an embodiment of the present invention which willnot be described in further detail, an information element for signalingthe CBS DRX level 1 information is extended, as shown in theillustration in FIG. 4, or new information elements are introduced.

This solution, therefore, defines the resource that is used for thetransmission of MBMS services, taking into account the backwardcompatibility. In comparison to known methods, physical channels otherthan the S-CCPCH, transport channels other than the FACH, and logicalchannels other than the CTCH are also used for the transmission of MBMSservices.

The resources which are used for the transmission of MBMS services aredefined by an extension, which likewise is not described in furtherdetail, of the information element (which is illustrated in theillustration in FIG. 5) for signaling the BMC scheduling message on thebasis of CBS DRX level 2. In this case, in particular, a configurationof the resources is largely released. The characteristics of thephysical channels, transport channels and logical channels and theparameters for assignment of the resources are added to, so that it isnow possible to state freely within a wide range when and which of theconfigured resources will be allocated for which MBMS group.

Although the present invention has been described with reference tospecific embodiments, those of skill in the art will recognize thatchanges may be made thereto without departing from the spirit and scopeof the present invention as set forth in the hereafter appended claims.

Background details relating, inter alia, to the protocols dealt with inthe present application can be found, in summarized form, in thefollowing references:

-   -   [1] 3GPP 25.211, Physical Channels and mapping of transport        channels onto physical channels, Release 99.    -   [2] Walke, B.: Mobilfunknetze und ihre Protokolle [Mobile radio        networks and their protocols], Volume 1, Teubner Verlag GmbH,        Wiesbaden 2000.    -   [3] 3GPP TS 25.331 V3.6.0, RRC Protocol Specification, Release        1999.    -   [4] 3GPP TS 25.324 V3.4.0, Broadcast/Multicast Control BMC,        Release 1999.

1. A method for transmitting multimedia messages of various sizes in aradio communication system via Multimedia Broadcast Multicast Serviceusing a multilayer protocol architecture from a sender via multipletransmission channels to a multicast group of receivers in the radiocommunication system, wherein each transmission channel is one of alogical channel, a transport channel, and a physical channel, whereinthe radio communication system allows for discontinuous data receptionby the receivers, and wherein transmitting a variable sized multimediamessage to the multicast group via Multimedia Broadcast MulticastService comprises: assigning indices to sets of resources in the radiocommunication system for communicating data; sending at least one firstplanning message via at least one first transmission channel, whereinthe at least one first planning message identifies at which times atleast one second transmission channel is reserved or assigned for thetransmission of further planning information regarding the sending ofthe variable-sized multimedia message; and sending at least one secondplanning message via the at least one second transmission channel at oneor more of the identified times in which the at least one secondtransmission channel is reserved or assigned, wherein the at least onesecond planning message identifies one or more third transmissionchannels that are actually used for transmission of the variable-sizedmultimedia message, and identifies a multicast group address or amulticast group identity corresponding to the multicast group; whereinthe previously assigned indices are used as the basis for notifying thereceivers as to the time and the particular resources upon which thevariable-sized multimedia message will actually be transmitted to thereceivers.
 2. The method according to claim 1, wherein the method isperformed as one of (1) an extension to a broadcast service bymultimedia transmission, and (2) a multicast service.
 3. The methodaccording to claim 2, wherein information about a respective recipientgroup is attached to at least one of the first and second planningmessages.
 4. The method according to claim 3, wherein recipient groupsare indicated by a recipient group address or a recipient groupidentity.
 5. The method according to claim 2, wherein information abouta multicast group is attached to at least one of the first and secondplanning messages.
 6. The method according to claim 1, wherein indicesare used as the basis for notifying when second planning messages areactually transmitted on second transmission channels, wherein saidindices have been previously assigned.
 7. The method according to claim1, wherein the first message further indicates which frames of thetransmission channels are reserved for the transmission of data.
 8. Themethod according to claim 1, wherein the one or more third transmissionchannels comprises a subset of the one or more second transmissionchannels.
 9. A telecommunication apparatus for transmitting multimediamessages of various sizes in a radio communication system via MultimediaBroadcast Multicast Service using a multilayer protocol architecturefrom a sender via multiple, transmission channels to a multicast groupof receivers in the radio communication system, wherein eachtransmission channel is one of a logical channel, a transport channel,and a physical channel, and wherein the radio communication systemallows for discontinuous data reception by the receivers, thetelecommunication apparatus configured to transmit a variable sizedmultimedia message to the multicast group via Multimedia BroadcastMulticast Service, including: assigning indices to sets of resources inthe radio communication system for communicating data; sending at leastone first planning message via at least one first transmission channel,wherein the at least one first planning message identifies at whichtimes at least one second transmission channel is reserved or assignedfor the transmission of further planning information regarding thesending of the variable-sized multimedia message; and sending at leastone second planning message via the at least one second transmissionchannel at one or more of the identified times in which the at least onesecond transmission channel is reserved or assigned, wherein the atleast one second planning message identifies one or more thirdtransmission channels that are actually used for transmission of thevariable sized multimedia message, and identifies a multicast groupaddress or a multicast group identity corresponding to the multicastgroup; wherein the previously assigned indices are used as the basis fornotifying the receivers as to the time and the particular resources uponwhich the variable sized multimedia message will actually be transmittedto the receivers.
 10. The telecommunication apparatus according to claim9, wherein the transmission of data is performed as one of (1) anextension to a broadcast service by multimedia transmission, and (2) amulticast service.
 11. The telecommunication apparatus according toclaim 10, wherein information about a respective recipient group isattached to at least one of the first and second planning messages. 12.The telecommunication apparatus according to claim 11, wherein recipientgroups are indicated by one of a recipient group address and a recipientgroup identity.
 13. The telecommunication apparatus according to claim10, wherein information about a multicast group is attached to at leastone of the first and second planning messages.
 14. The telecommunicationapparatus according to claim 9, wherein indices are used as the basisfor notifying when second planning messages are actually transmitted onsecond transmission channels, wherein said indices have been previouslyassigned.
 15. The telecommunication apparatus according to claim 9,wherein the first message further indicates which frames of thetransmission channels are reserved for the transmission of data.
 16. Thetelecommunication apparatus according to claim 9, wherein the one ormore third transmission channels comprises a subset of the one or moresecond transmission channels.
 17. A method for transmitting multimediamessages of various sizes in a radio communication system via MultimediaBroadcast Multicast Service using a multilayer protocol architecturefrom a sender via multiple transmission channels to a multicast group ofreceivers in the radio communication system, wherein each transmissionchannel is one of a logical channel, a transport channel, and a physicalchannel, wherein the radio communication system allows for discontinuousdata reception by the receivers, and wherein transmitting a variablesized multimedia message to the multicast group via Multimedia BroadcastMulticast Service comprises: sending at least one first planning messagevia at least one first transmission channel, wherein the at least onefirst planning message identifies at which times at least one secondtransmission channel is reserved or assigned for the transmission offurther planning information regarding the sending of the variable-sizedmultimedia message; and sending at least one second planning message viathe at least one second transmission channel at one or more of theidentified times in which the at least one second transmission channelis reserved or assigned, wherein the at least one second planningmessage identifies one or more third transmission channels that areactually used for transmission of the variable-sized multimedia message,and identifies a multicast group address or a multicast group identitycorresponding to the multicast group.